Conventional processes for producing certain types of semiconductor components having plastic housings typically involve separating individual semiconductor chips from a common semiconductor wafer. Such semiconductor chips may, for example, have active top surfaces and back surfaces, with the active top surfaces having contact surfaces. Once separated, the semiconductor chips can be mounted on a mold plate. A common carrier is then produced from a plastic embedding compound on the mold plate, and rewiring lines and outer contact surfaces are produced. The common carrier is then divided into the individual semiconductor components.
A process of this type is known, for example, from DE 101 37 184 A1, which describes a process in which the active surface of the singulated semiconductor components is mounted on an adhesive film, which is in turn stretched over a carrier frame. This arrangement is then encapsulated with a synthetic resin, which can be done, for example, using a wafer molding process, a printing process, or similar known processes. The plastic compound is then cured. The film is subsequently pulled off again, and the matrix of semiconductor chips, which have in the meantime been embedded in the common plastic carrier, is removed from the carrier frame. The “reconstituted” semiconductor wafer produced in this way is then used as a starting material for the rewiring processes, as they are known.
The process described above has the fundamental advantages of using very low-cost materials and very efficient process steps. The direct embedding or direct encapsulation of the semiconductor chip with a plastic makes this technology, which is known from the prior art, very versatile, i.e., this technology can be used to process a very wide range of semiconductor chip sizes and to produce a very wide range of housing sizes. It is possible to produce large panels in wafer form which allow further processing using conventional equipment.
However, one major drawback of this known process is that the film material restricts the positional accuracy of the semiconductor chips on the encapsulated wafer. This positional accuracy of the embedded semiconductor chips is adversely affected by various effects. First, the carrier film has only a very limited dimensional stability. Storage, handling and processing of the carrier film cause deformation of the latter. Deformation of this type includes, for example, the formation of creases and relaxation. This formation of creases and relaxation in turn leads to the individual semiconductor chips shifting on the film.
Since the encapsulation process, generally wafer molding, is performed at high temperatures, i.e., at temperatures of up to 180° C., deformation also occurs during that process. The deformation which occurs during the encapsulation process is generally even greater than the deformation of the carrier film caused by storage, handling, and processing of the carrier film. The plastic film generally becomes soft in the temperature ranges above 100° C. up to 180° C. This softening further reduces its stability.
Uniform lamination of the film onto the carrier frame is only achievable with difficulty. An inhomogeneous tension in the film leads to uncontrollable shifts in the semiconductor chips.
Heretofore, there has been no suitable replacement for the films since conversely the film-typical properties of the films are required when separating the chip carrier from the base carrier. Properties which play an important role in this context and are virtually irreplaceable are the delamination ability inherent to a film. A film, unlike more robust carrier materials, can be pulled or peeled off.
If a robust, more stable carrier were to be used as a film replacement, complete separation of the two carriers following the encapsulation process would be very difficult, on account of the excessively high bonding force and the large surface areas. Accordingly, there is a need to provide a new production process and a new carrier that avoids the drawbacks of the films currently in use.